The invention relates to needle protecting devices for injection devices. It also relates to methods of making and assembling a needle protecting device, and to methods of using a needle protection device and an injection device equipped with a needle protection device. In one embodiment, while in a protective position, the needle holder in accordance with the present invention surrounds the injection needle of an injection device and prevents the needle from being unintentionally exposed.
An injection device comprising a needle protecting device is known from U.S. Pat. No. 5,609,577. An injection needle is surrounded by a needle protecting sleeve. The needle protecting sleeve is mounted, axially slidably, on a casing of the injection device. In the protective position, the needle protecting sleeve is secured by a block against the injection needle being unintentionally slid or exposed. Once the block is released, the needle protecting sleeve can be slid into a rear position in which the injection needle protrudes freely beyond the retracted needle protecting sleeve. When the needle protecting sleeve is retracted, a tension spring of the needle protecting device is tensed. If the needle protecting sleeve is relaxed after the injection, then the needle protecting sleeve pre-latches back into its protective position under the tension stress of the tension spring. The blocking mesh or connection is automatically re-established in the protective position.
The block is formed by a cam and a guideway for the cam. The guideway consists of one section extending axially, and another section connected to it at a right angle. In the protective position, the cam meshes with the angled section of the guideway. In this way, the needle protecting sleeve is prevented from sliding and exposing the injection needle. For releasing the block, the needle protecting sleeve is rotated relative to the base body until the cam comes to rest in the axially extending section of the guideway. In this rotational position, the needle protecting sleeve can be slid relative to the base body, into the rear position. The tension spring does not only serve to pre-tension the needle protecting sleeve into the front position. Simultaneously, it also tenses the needle protecting sleeve into the rotational position in which the cam abuts in the angled section of the guideway. Thus, for injecting, the needle protecting sleeve is first rotated against the force of the tension spring and then, likewise against the force of the tension spring, slid into its rear position.
In the known needle protecting device of the '577 patent, the tension spring is a substantial element of the block. By using a spring to secure the needle protecting sleeve in its protective position, a complicated construction is required for the blocking mechanism. Furthermore, the normal functioning of the blocking mechanism is substantially dependent on the spring. The spring can for instance break or jam. If the spring malfunctions, it cannot be guaranteed that the needle protecting sleeve is securely blocked.